Variable resistance



UNITED STATES PATENT OFFICE,

THEODORE W. CASE, OF SCIPIO, NEW YORK.

VARIABLE RESISTANCE.

No Drawing.

7 '0 all whom it may concern Be it known that I, THEODORE W. CAsE, a citizen of the United States of America, and resident of Scipio, in the county of Cayuga and State of New York, have invented new and useful Improvements in Variable Resistances, of which the following is a full, clear, and exact description.

This invention relates to certain improvements in variable resistances, and specifically contemplates a material as an element of an electric circuit, subject to thecondition that variations in light produce a corresponding variation in the electrical resistance of the element, thereby effecting a change of current in accordance With variations of light intensity to which the element is exposed.

The object, therefore, of the invention is the production of a material or compound adapted to form a portion of an electric circuit or conductor, the resistance of which diminishes as the intensity of the light to which it is exposed increases.

' I have discovered that a material consist-. ing of a compound of thallium and iodin, can be utilized as a portion of an electric circuit, and that its resistance to the passage of currents through said circuit varies under the influence of lightto efiect a change of current in accordance with the intensity of the light rays to which the substance is subjected, and that a compound of thallium and iodin is peculiarly efficient for this purpose and 7 highly sensitive to variation of light intensity due to the fact that the ratio of chang or percentage change of its resistance to the passage of an electric current under variations of light intensity is very great.

An interesting phenomenon of the invention consists in the fact that the electrical resistance of the material specified is varied by rays of light invisible to the human eye, such variation 'of current being readily Specification of Letters Patent.

Application filed October 9, 1917. Serial No. 195,652.

Patented July 8, 1919.

demonstrated and measured by known a-pparatus. This variation in resistance is maximum in the ultra violet region of the spectrum.

The material, compound or resistance element may be incorporated in an electric circuit in any suitable way, and such element may constitute any portion or part of such circuit and when so embodied the compound may be supported in any suitable way for contact and exposure to light rays.

The invention is adapted for and may be applied to various uses, as, for instance, in the detection of ultra violet radiations, and I, therefore, desire to broadly claim the same without restriction as to the method, manner or condition of use and without limitations as to the addition of any other elements to the material or compound so long as the same do not destroy the utility of the material for this purpose or anv other purpose, and I desire to claim the material for use with either direct or alternating current. or a pulsating direct current. .The expression light rays, as used in the specification and claims hereof, is deemed to include both visible and invisible rays.

What I claim is:

1. A resistance element formed of a compound of. thallium-'andiodin.

2. A resistanceelement formed of a compound comprising thallium and iodin.

3. A resistance element formed of a material comprising a compound of thallium and iodin.

4. An electric circuit having a portion supported for exposure to light rays, such portion comprising a compound of thallium and iodin.

THEODORE W. CASE.

Witnesses:

E. A. THOMPSON, E. D. SPONABLE. 

